Health and Medicine

First Human Embryos Created After Implantation

Human Embryo

Scientists at the University of Cambridge have developed a new procedure that allows embryos to grow in vitro well past the implantation stage, which is thus far when an embryo would have to be placed inside a womb in order to continue to survive.

These new findings allow scientists to get a close look at the earliest stages of the development of human embryos, beginning as early on as 13 days following fertilization. This research holds the potential to improve chances of successful in vitro fertilization (IVF).

Upon fertilization, an egg divides to create a small ball of stem cells. At day three, the cells cluster inside the embryo, a stage called blastocyst. This period prior to implantation has been studied in depth with in vitro culture methods. As of day seven, implantation into the uterus is critical for the survival of the embryo. Improper implantation or a fail to implant are the largest causes of pregnancy loss today, but there is not enough research as of yet to help understand cell and molecule changes that may be leading to these sudden ends of pregnancy. Studies cannot be conducted on embryos inside of the womb and until these new findings; there has not been a known way to culture human embryos inside a lab past day seven.

Studies published in Nature journal and Nature Cell Biology journal share the findings of two international teams that explains a new technique that offers scientists the ability to culture embryos outside of the womb up until the 13th development day. The scientists used data previously recorded by Professor Magdalena Zernicka-Goetz and his team from the University of Cambridge to assist them in being able to recreate the reorganization an embryo experiences upon being implanted within the lab.

Human embryo in the absence of maternal tissues on day 10 (left) and day 11 (right)
Image Credit: Zernick-Goetz lab, University of Cambridge

Author of both studies, Professor Zernicka-Goetz led the UK research, saying embryos really begin to take shape after implantation, when the body plan (including any defects) is “decided”. He says the study creates a unique opportunity for a much more in depth understanding of human development and what may occur during these very important stages that so often lead to pregnancy compications. Dr. Marta Shahbazi, a co-author of the study says the new data does not completely allow for full access to the secrets of the development of the human body, but it does allow researchers to get a true look at just how much our blastocysts reorganize during early growth.

Using their new system for in vitro culture of human embryos, researchers were able to watch as the three types of cells that make up the blastocyst reconstruct themselves completely directly following implantation. Professor Zernicka-Goetz says the stem cells within the epiblast build a cavity through their reorganization. This cavity is imperative to the further development of the embryo and was previously believed to appear due to the death of surrounding cells, but this new information proves that cells do not need to die off in order to build the necessary pocket. The professor states that the process is very similar to what has been seen in mouse embryos, although the structures are not the same. This means the process may be something that occurs in a wide range of species.

At this time only about a fourth of IVF cases are successful and Dr. Simon Fishel, founder and President of the CARE Fertility Group believes as these processes are further understood, IVF could improve. The research would not have been possible without IVF patients who donated their embryos.